You can use {% cache globally using key craft.request.path %} to cache based on the request URI if you'd like.

Why would you do this? Andrew Welch mentioned in Slack that "if you have spambots hitting your page or unique identifiers in the query string from Google Adwords or any number other such things, the default {% cache %} tag can result in a massive number of entries in your template caches, which has a horrible impact on TTFB."